textproduct: Quad Cities

KEY MESSAGES

- The wet weather pattern will continue through the weekend with rounds of rain which may be heavy at times. There will be periods of dry weather between each round.

- There is a Marginal Risk, Level 1 out of 5, for isolated severe storms along the I-380 corridor this afternoon and for areas south of Highway 20 on Saturday. Primary severe hazard each day will be damaging winds.

- A Flood Watch has been issued for portions of east-central Iowa and far northwestern Illinois for late tonight through Saturday evening. Rainfall totals of 1-3 inches are likely (60-80%) in these areas with the potential (10-20%) for localized areas of 3+ inches.

- The repeated rounds of rain will keep the risk of flash flooding around through Sunday. Rapid rises on small creeks and streams and the flooding of low-lying areas are possible.

SHORT TERM /THROUGH SATURDAY/

Issued at 219 AM CDT Fri Sep 18 2026

A mid-level trough over the Northern Plains is forecasted to pull a low pressure over Nebraska eastward towards Iowa. WAA and F-gen in the 850-to-700 mb layer will support scattered showers and storms (30-60% coverage) to develop late this morning across eastern Iowa and far northwest Illinois and last into the afternoon. The quick motion of this rain band should keep rainfall totals low, ranging between 0.1-0.25 of an inch, with isolated spots over half an inch. There is a Marginal Risk, Level 1 out of 5, for an isolated severe storms near the I-380 corridor. While storms are expected to be elevated, a few storms near the warm front over central Iowa may be able to produce surface gusts where DCAPE is able to exceed 750 J/kg.

By tonight, the low moves into western Iowa, lifting the warm front towards the I-80 corridor in eastern Iowa. Another round of heavy rain and thunderstorms north of I-80 is expected to develop after midnight in response to the enhanced surface convergence, low-level isentropic upglide, and near record level PWATs around 2 inches. A Flood Watch has been issued for portions of east-central Iowa and far northwestern Illinois where 1-3 inches of rainfall is likely (60-80%) with localized areas of 3+ inches possible (10-20%). This Watch could be expanded to the southwest if CAM guidance continues to show storms backbuilding along the WAA wing.

Heading into Saturday, a shortwave trough moves into the Northern Rockies, pulling another weak subtropical trough northeastward towards Iowa. The low pressure continues to trek eastward into our outlook area, keeping scattered showers and storms (50-80% coverage) around. With dew points in the low-to-mid-70s areawide and slightly steeper mid-level lapse rates, SBCAPE will likely (60-80%) exceed 1500 J/kg along and south of Highway 30, enabling stronger storms to potentially produce water-loaded downbursts. The SPC has a Marginal Risk, Level 1 out of 5, for isolated severe storms south of Highway 20 with damaging winds as the primary hazard.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 219 AM CDT Fri Sep 18 2026

Saturday Night-Sunday...After sunset, a developing high pressure over central Canada nudges the surface trough southeastward into Illinois Saturday night. Despite the low- level CAA, another band of moderate-to-heavy rainfall will likely (70-90%) develop and persist into Sunday. While there is still uncertainty among the ensemble models on placement of the heaviest axis, general consensus is showing rainfall totals of 0.25- 0.75 of an inch (50-80% chance) across a broad area with a swath of 1-2 inches possible (30-50%). The coverage and intensity of these showers should begin to decrease by Sunday afternoon as dry air advection occurs near the surface.

Sunday Night-Tuesday...The main trough over the Northern Rockies finally reaches the Northern Plains as low-to-mid-level ridging over south-central Canada continues to push the surface trough further south into the lower Ohio River Valley. Despite the cold air advection, CVA ahead of the trough keeps scattered light-to-moderate showers (50-70% coverage) around Sunday night into Monday. By Monday night, the trough finally reaches Iowa as cold-core showers form underneath, keeping PoPs around through Tuesday morning. As subsidence sets in on the backside of the trough and high pressure builds in from the north, the outlook area should be rain-free by Tuesday evening.

Wednesday-Thursday...Fall-like weather is likely (70-90%) to return for the middle of next week. Confluence aloft and surface high pressure is forecasted to keep Wednesday and Thursday dry as CAA keeps temperatures below average with highs in the mid-60s to low 70s and lows in the mid-40s to low 50s.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1245 PM CDT Fri Sep 18 2026

Active weather is expected today into Saturday morning with periods of MVFR/IFR ceilings and rounds of showers and thunderstorms. After some improvement in ceilings this afternoon/evening, conditions will deteriorate into tonight with MVFR/IFR likely north of BRL. Scattered showers and isolated storms are then expected late tonight into Saturday AM, most favored at DBQ and CID. Heavy downpours are likely with the strongest cells which could lead to brief visibility reductions under 1 mile. A return to VFR/MVFR is anticipate by mid/late Saturday morning as rain coverage decreases across the area.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Flood Watch from late tonight through Saturday evening for IAZ040>042-054. IL...Flood Watch from late tonight through Saturday evening for ILZ001-002-007. MO...None.